Test tube rack



FIG. 1 is a top perspective view of a test tube rack, showing my new design, the bottom perspective view being a mirror image;

FIG. 2 is a top plan view thereof;

FIG. 3 is a side elevational view thereof, the opposite side elevational view being a mirror image; and,

FIG. 4 is an end elevational view thereof, the opposite end elevational view being a mirror image. 

The ornamental design for a test tube rack, as shown. 